1. Field of the Invention
The present invention relates to an airbag apparatus for an automobile for protecting a person in a vehicle such as a car; for example, a driver or a passenger sitting in the front passenger seat, from impact upon head-on or side collision of the vehicle to thereby ensure safety of the person. More particularly, the invention relates to an improvement in the structure of reinforcement for a surface panel, such as an instrument panel cover to be fractured upon inflation of an airbag.
2. Description of the Related Art
An airbag apparatus for a front passenger seat or a driver seat of a vehicle, such as a car, or that to be mounted on a side pillar of the vehicle basically includes an airbag, an airbag case for accommodating the folded airbag, and an inflater for inflating the airbag. The airbag apparatus is disposed inside an instrument panel cover of the vehicle.
Generally, an instrument panel cover of a car is made of a synthetic resin, such as polypropylene, and covers the surface of an instrument panel core formed integrally from a synthetic resin, such as polypropylene.
A conventional airbag apparatus for a front passenger seat will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view showing a conventional instrument panel cover having a fracture-opening section for allowing an inflating airbag to project outward therethrough. FIG. 2 is a schematic sectional view taken along line IIxe2x80x94II of FIG. 1.
Referring to FIGS. 1 and 2, an airbag apparatus for a front passenger seat 1 includes an airbag case 5 adapted to accommodate a folded airbag 4, which is inflated by means of gas from an inflater. The airbag case 5 is disposed behind a substantially horizontal surface 3a of an instrument panel cover 3 in the vicinity of a windshield 1a of a car.
The airbag case 5 has an opening portion 5a formed in opposition to the inside surface of the instrument panel cover 3. A flexible fracture-opening lid 6 formed of a synthetic resin is disposed at an opening portion 3b formed on the instrument panel cover 3 in opposition to the opening portion 5a of the airbag case 5, so as to cover the opening portion 3b. Upon inflation of the airbag 4, the fracture-opening lid 6 is split open in a casement condition through fracture along a center groove 6a and peripheral grooves 6b, which are formed on the inside surface of the fracture-opening lid 6 in opposition to the opening portion 5a of the airbag case 5. The inflating airbag 4 projects outward through the thus-formed opening.
A mounting leg portion 7 and a plurality of engagement pieces 8 are formed on the inside surface of the fracture-opening lid 6. The mounting leg portion 7 assumes the form of a rectangular frame slightly greater in size than the opening portion 5a of the airbag case 5. The engagement pieces 8 are elastically engaged with the edge of the opening portion 3b of the instrument panel cover 3. A plurality of rectangular through-holes 7c are formed in a front wall 7a of and in a rear wall 7b of the mounting leg portion 7. The rectangular through-holes 7c are engaged with corresponding hooks 9 provided on a front wall 5b and a rear wall 5b of the opening portion 5a of the airbag case 5, thereby attaching the fracture-opening lid 6 to the opening portion 3b of the instrument panel cover 3.
When, upon inflation of the airbag 4, the fracture-opening lid 6 is split open in a casement condition through fracture along the center groove 6a and the peripheral grooves 6b, the rectangular through-holes 7c formed in the front and rear walls 7a and 7b of the mounting leg portion 7 are engaged with the hooks 9 provided on the front and rear walls 5b of the opening portion 5a of the airbag case 5, thereby preventing scattering of the fracture pieces of the fracture opening lid 6.
According to the airbag apparatus for a front passenger seat shown in FIG. 1, the opening portion 3b is formed in the instrument panel cover 3 in such a manner as to face the opening portion 5a of the airbag case 5. The fracture-opening lid 6 is a discrete element different from the instrument panel cover 3 and made of a flexible resin material and is fitted to the opening portion 3b. Thus, the manufacture and the assembly work of the instrument panel cover 3 and the fracture-opening lid 6 are rather complicated. Also, the fracture-opening lid 6 easily deforms when an external force is applied thereto, and encounters difficulty in matching color with the instrument panel cover 3 because it is made of material different from that of the instrument panel cover 3, thereby damaging the appearance or design of the instrument panel cover 3.
In order to solve the above-mentioned problems, there has been proposed a seamless-type airbag apparatus for a front passenger seat. The airbag apparatus does not employ a discrete fracture-opening lid, and therefore a fracture line of an opening portion of an instrument panel cover is invisible.
The proposed airbag apparatus is shown in FIGS. 3 and 4. FIG. 3 is a schematic perspective view showing a single-plate-type instrument panel cover 3 having a fracture-opening section 30 for allowing an inflating airbag to project outward therethrough. FIG. 4 is a schematic sectional view taken along line IVxe2x80x94IV of FIG. 3.
As shown in FIGS. 3 and 4, hinge grooves 30a and fracture grooves 30b and 30c are formed on the inside surface of the instrument panel cover 3 by use of a laser. Specifically, a pulsating laser beam is perpendicularly applied to the inside surface of the instrument panel cover 3 while being moved along peripheral portions of reinforcement plate members 10 fixed to the inside surface, thereby forming the grooves 30a, 30b, and 30c; i.e., forming the fracture-opening section 30 having a size corresponding to that of the opening portion 5a of the airbag case 5 and adapted to allow an inflating airbag to project outward therethrough.
The longitudinally formed fracture groove 30b and the fracture grooves 30c formed perpendicularly to the fracture groove 30b divide the fracture-opening section 30 into a front fracture-opening subsection 31 and a rear fracture-opening subsection 32. Upon inflation of an airbag, the fracture-opening subsections 31 and 32 are split apart from each other in a casement condition (in opposite directions) while hinging on the hinge grooves 30a. 
When, upon inflation of an airbag, the fracture-opening section 30 of the instrument panel cover 3 is split open by pressure of the inflating airbag 4, the hinge groove 30a may be broken with a resultant separation of the fracture-opening subsections 31 and 32 from the instrument panel cover 3. In order to avoid this problem, the paired reinforcement plate members 10 are provided on the inside surface of the fracture-opening section 30 of the instrument panel cover 3. Specifically, horizontal first end portions of the reinforcement plate members 10 are fixedly attached to the inside surface of the fracture-opening section 30 through thermal joining or like processing. Second end portions 10a of the reinforcement plate members 10 are bent at their hinge portions 11 and extend downward along the inner surfaces of front and rear walls of a frame-shaped reinforcement rib 12 projecting integrally from the inside surface of the instrument panel cover 3. The front and rear walls of the reinforcement rib 12 and corresponding second end portions 10a of the reinforcement plate members 10 are engaged with corresponding hooks 36 attached to front and rear walls 5b of the airbag case 5. The inside distance between the second end portions 10a is slightly greater than a corresponding outer size of the opening portion 5a of the airbag case 5. The reinforcement plates 10 prevent scattering of the fracture-opening subsections 31 and 32 of the fracture-opening section 30 of the instrument panel cover 3 upon inflation of an airbag, thereby solving a problem involved in the conventional airbag apparatus having the discrete fracture-opening lid 6.
In order to allow the fracture-opening subsections 31 and 32 to be split open smoothly, hook engagement holes 10b formed in the corresponding second end portions 10a of the paired reinforcement plate members 10 assume a sufficiently large size so as to allow upward movement of the second end portions 10a when the fracture-opening subsections 31 and 32 are split open. Reference numeral 13 denotes a thin-walled portion of the reinforcement rib 12 at which the reinforcement rib 12 and the instrument panel cover 3 are integrated together. The thin-walled portion 13 is adapted to prevent formation of a sink mark on the front surface of the instrument panel cover 3 when the instrument panel cover 3 is molded.
The thus-configured airbag apparatus for a front passenger seat functions in the following manner. Upon collision of the vehicle, an impact force caused by the collision is detected by a sensor. A control unit including a CPU judges whether or not the detected impact force is equal to or higher than a predetermined value. When the control unit judges that the impact force is not lower than the predetermined value, the control unit issues a signal for causing the inflater to generate a predetermined gas. The gas is fed to the airbag so as to promptly inflate the airbag.
The inflating airbag presses, from inside, the fracture-opening section 30 of the instrument panel cover 3. The fracture-opening section 30 is fractured along the fracture grooves 30b and 30c in a casement condition.
The thus-fractured front and rear fracture-opening subsections 31 and 32 are opened outward while being turned inside out about the hinge portions 11 of the reinforcement plate members 10. Simultaneously, the inflating airbag 4 projects outward from the instrument panel cover 3 through the thus-formed opening in the instrument panel cover 3. Serving as a cushion, the inflated airbag 4 supports a front seat passenger at his/her chest and head, thereby protecting the passenger from the impact force of collision.
In the above-described airbag apparatus, the reinforcement plate members 10 and the reinforcement rib 12 are provided on the inside surface of the instrument panel cover 3 in a peripheral region around the fracture-opening section 30. However, in order to facilitate the installation work of the airbag case 5 and fracture-opening of the fracture-opening subsections 31 and 32, vertical play is provided at engagements of the reinforcement plate members 10 and the reinforcement rib 12 with the hooks 36. That is, the reinforcement plate members 10 and the reinforcement rib 12 are not configured to support a pressing force imposed from above; i.e., a pressing force imposed on the instrument panel cover 3. If a load is mistakenly imposed on the instrument panel cover 3, the hinge grooves 30a and/or the fracture grooves 30b and 30c may be fractured. As a result, the fracture-opening section 30 is dented or the peripheral edge of the fracture-opening section 30 is deformed, thereby damaging the appearance of the instrument panel cover 3.
In the fracture-opening section 30 of the improved instrument panel cover 3, the fracture grooves 30b and 30c are formed on the inside surface of the instrument panel cover 3; the reinforcement plate members 10 are fixedly attached to the inside surface of the fracture-opening section 30 through thermal joining while being located on opposite sides of the fracture groove 30b with respect to the front-rear direction of the fracture-opening section 30; and each of the fracture grooves 30c is located between the reinforcement plate members 10 and the reinforcement rib 12. Thus, upon inflation of an airbag, the fracture-opening section 30 is split open smoothly along the fracture grooves 30b and 30c. Therefore, formation of a sharp edge or a like problem is not involved. However, in the case where the instrument panel cover 3 has a certain shape, molding of the instrument panel cover 3 must employ a slide mold for formation of the reinforcement rib 12. Also, since the height of the reinforcement rib 12 projecting perpendicularly from the instrument panel cover 3 is large as compared with the wall thickness of the instrument panel cover 3, when the reinforcement rib 12 shrinks in the course of cooling after withdrawal of a mold, a sink mark tends to arise on the front surface of the instrument panel cover 3 at a position corresponding to the reinforcement rib 12. Therefore, various measures must be taken against occurrence of a sink mark.
As shown in FIG. 5, the reinforcement plate members 10 for the fracture-opening section 30 in the conventional airbag apparatus are each formed from a single metal plate. Protrusions 31A arranged uniformly on the entire inside surface of the fracture-opening section 30 are fitted into elongated holes 10d that are formed in the reinforcement plate members 10 and arranged in the same pattern as that of the protrusions 31A. The protrusions 31A projecting from the corresponding elongated holes 10d are melted through application of heat to thereby be engaged with the reinforcement plate members 10. Thus, the reinforcement plate members 10 are unitarily fixed to the fracture-opening section 30 made of a synthetic resin. However, this structure involves the following problem: when temperature variations cause a large expansion/shrinkage difference between the reinforcement plate members 10 and the fracture-opening section 30, the difference cannot be absorbed. As a result, the surface of the instrument panel cover 3 including the fracture-opening section 30 is undulated, thereby damaging the appearance of the instrument panel cover 3.
Also, when a tensile stress induced by the above-mentioned expansion/shrinkage difference is imposed on thermally joined portions between the reinforcement plate members 10 and the fracture-opening section 30, the thermally joined portions may be partially fractured, with a resultant partial separation of the reinforcement plate member 10 from the fracture-opening section 30. As a result, upon inflation of an airbag, the following problems may arise: the fracture-opening section 30 fails to be properly fractured along the fracture grooves 30b and 30c; the reinforcement plate members 10 fail to be smoothly opened apart from each other about their hinge portions 11; edge portions of an opening formed after fracture of the fracture-opening section 30 are burred or cracked; and in the worst case, the fracture-opening section 30 is scattered in pieces.
When an external impact force is locally applied to the fracture-opening section 30, the impact force is imposed on thermally joined portions between the reinforcement plate members 10 and the fracture-opening section 30. As a result, the thermally joined portions may be partially fractured.
An object of the present invention is to solve the above-mentioned problems in the conventional airbag apparatus for an automobile and to provide an airbag apparatus for an automobile exhibiting improved resistance to a pressing load imposed externally on a fracture-opening section and its peripheral region of a surface panel covering an instrument panel region, a side pillar region, or a central portion of a steering wheel of a vehicle; facilitating attachment of an airbag case and relevant components to the inside surface of the surface panel; not requiring formation of a reinforcement rib around the fracture-opening section; being unlikely to form a sharp edge at a fracture surface of the fracture-opening section; and facilitating, during scrapping a car, removal of airbag components, particularly an inflater, which is categorized as industrial waste.
Another object of the present invention is to provide an airbag apparatus for an automobile exhibiting improved resistance to a pressing load imposed externally on a fracture-opening section and its peripheral region of a surface panel covering an instrument panel region, a side pillar region, or a central portion of a steering wheel of a vehicle, and capable of absorbing an external force imposed on the fracture-opening section and a thermal expansion/shrinkage difference between the fracture-opening section and a reinforcement plate member for the fracture-opening section.
To achieve the above objects, an airbag apparatus for an automobile of the present invention comprises a frame member having an edge portion for reinforcing the surface panel from inside, the edge portion being in close contact with or in the vicinity of a peripheral region around the fracture-opening section of the surface panel. Thus, even when a pressing force is imposed on the upper surface of the surface panel, the edge portion of the frame member supports from underneath a region of the fracture-opening section including fracture grooves and hinge grooves, thereby preventing occurrence of a dent in the fracture-opening section and deformation of the peripheral edge of a potential opening of the fracture-opening section. Also, since the frame member and the reinforcement plate member are configured as a single unit, attachment to the inside surface of the surface panel is facilitated.
According to the present invention, rest segments formed at the edge portion of the frame member support from underneath the fracture-opening section and a peripheral region around a potential opening of the fracture-opening section, thereby more reliably preventing occurrence of a dent in the fracture-opening section and deformation of the peripheral edge of the potential opening of the fracture-opening section.
According to the present invention, joint segments are fixedly attached to a peripheral region around a potential opening of the fracture-opening section. Thus, in cooperation with the rest segments, the joint segments reinforce the peripheral edge of the potential opening of the fracture-opening section without employment of a reinforcement rib, thereby preventing formation of a sharp edge at, or a partly detached piece from, a fracture portion of the fractured fracture-opening section upon inflation of an airbag and thus providing a neat fracture surface.
According to the present invention, an airbag support member is separably connected to the frame member. Thus, when a car is to be scrapped, the airbag support member can be easily detached from the frame member, so that an inflater and other relevant components can be easily removed for proper disposal to thereby prevent potential environmental contamination.
According to the present invention, thermal joint protrusions are integrally formed on the inside surface of the fracture-opening section and inserted through through-holes formed in the reinforcement plates. The inserted thermal joint protrusions are melted and crushed to thereby firmly join the reinforcement plates and the fracture-opening section.
According to the present invention, a tentative fixing member is provided for tentatively fixing the reinforcement plates in place when the reinforcement plates and the fracture-opening section are to be joined through melting of the thermal joint protrusions.
According to the present invention, a plurality of slits are formed in the reinforcement plate member. The slits function to absorb a thermal expansion difference between the reinforcement plate member and the fracture-opening section. Thus, even when the reinforcement plate member and the fracture-opening section are exposed to a high-temperature atmosphere, fracture of thermal joint protrusions of resin joining them can be prevented.
According to the present invention, the reinforcement plate member is divided into a plurality of reinforcement segments arranged along the longitudinal direction of the fracture-opening section; the reinforcement segments are connected to the edge portion of the frame member by means of corresponding arcuate hinge portions; the reinforcement segments are fixedly attached to the fracture-opening section; and the adjacent reinforcement segments are connected by means of an elastic segment. The configuration functions to absorb a thermal expansion difference between the reinforcement segments and the fracture-opening section, as well as a difference in expansion/shrinkage therebetween caused by application of an external force, thereby preventing fracture of thermal joint protrusions of resin joining the reinforcement segments and the fracture-opening section, which would otherwise result from the thermal expansion difference or the difference in expansion/shrinkage. Also, the configuration allows the reinforcement segments to easily follow the deformation of the fracture-opening section upon inflation of an airbag, thereby preventing fracture of the thermal joint protrusions of resin and enabling the fracture-opening section to be smoothly split open.
According to the present invention, the frame member comprises joint portions extending outward, along the inside surface of the surface panel, from opposite sides of the edge portion of the frame member with respect to the longitudinal direction of the fracture-opening section; and the opposite joint portions are fixedly attached to the inside surface of the surface panel, thereby more reliably preventing occurrence of a dent in the fracture-opening section and deformation of the peripheral edge of the potential opening of the fracture-opening section.
According to the present invention, each of the joint portions is divided into a plurality of joint segments arranged along the lateral direction of the fracture-opening section; the joint segments are fixedly attached to the surface panel; and adjacent joint segments are connected by means of an elastic segment. Thus, even when an expansion/shrinkage difference between the surface panel and the joint portions of the frame member arises from an external cause, such as temperature variations, the joint portions can absorb such a difference, thereby preventing occurrence of undulation of the surface panel and thus maintaining the appearance of the surface panel intact.